U.S. patent number 9,767,995 [Application Number 15/008,488] was granted by the patent office on 2017-09-19 for plasma treatment device and method for plasma treatment.
This patent grant is currently assigned to Leibniz-Institut fuer Plasmaforschung und Technologie e.V.. The grantee listed for this patent is INP Greifswald e.V.. Invention is credited to Torsten Gerling, Norbert Lembke, Klaus-Dieter Weltmann.
United States Patent |
9,767,995 |
Gerling , et al. |
September 19, 2017 |
Plasma treatment device and method for plasma treatment
Abstract
A plasma treatment device having an electrode arrangement (3)
for generating a plasma in a supplied gas stream. The electrode
arrangement has at least one movably mounted electrode. The plasma
is preferably a cold atmospheric pressure plasma and can be
generated so as to vary in location by means of movement of the at
least one electrode.
Inventors: |
Gerling; Torsten (Greifswald,
DE), Lembke; Norbert (Greifswald, DE),
Weltmann; Klaus-Dieter (Ostseebad Binz, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
INP Greifswald e.V. |
Greifswald |
N/A |
DE |
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Assignee: |
Leibniz-Institut fuer
Plasmaforschung und Technologie e.V. (Greifswald,
DE)
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Family
ID: |
55272256 |
Appl.
No.: |
15/008,488 |
Filed: |
January 28, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160225589 A1 |
Aug 4, 2016 |
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Foreign Application Priority Data
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Jan 29, 2015 [DE] |
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10 2015 101 315 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J
37/32532 (20130101); H05H 1/48 (20130101); H05H
1/475 (20210501) |
Current International
Class: |
H01J
7/24 (20060101); H05B 31/26 (20060101); H01J
37/32 (20060101); H05H 1/48 (20060101) |
Field of
Search: |
;315/111.21,231.31 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101778525 |
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Jul 2010 |
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CN |
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10 2006 019 664 |
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Oct 2007 |
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DE |
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10 2009 028 190 |
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Feb 2011 |
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DE |
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10 2009 047 220 |
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Jun 2011 |
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DE |
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11 2011 105 333 |
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Mar 2014 |
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DE |
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10 2013 000 440 |
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Jul 2014 |
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DE |
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2 763 778 |
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Nov 1998 |
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FR |
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2 775 864 |
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Sep 1999 |
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FR |
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Primary Examiner: Taningco; Alexander H
Assistant Examiner: Garcia; Christian L
Attorney, Agent or Firm: Whitham, Curtis & Cook,
P.C.
Claims
The invention claimed is:
1. A plasma treatment device, comprising: an electrode arrangement
for generating a plasma; said electrode arrangement comprising at
least one movably mounted electrode which is a part of the
electrode arrangement, wherein the plasma can be generated so as to
vary in location by means of movement of the at least one movably
mounted electrode, wherein the at least one movably mounted
electrode is or includes at least one rod electrode disposed on a
carrier element so as to be rotatable about a rotation axis,
wherein the rod electrode extends in an offset manner in relation
to the rotation axis, in a direction parallel to the rotation axis,
or at an acute angle in relation to the rotation axis, and further
comprising a counter-electrode disposed adjacent to a tip of the
least one rod electrode, wherein the counter-electrode is a plate
having a plurality of openings disposed in a distributed manner on
at least one orbit, which is matched, respectively, to the orbit of
the tip of the at least one rod electrode.
2. The plasma treatment device according to claim 1, wherein the
counter-electrode is dielectric or dielectrically shielded.
3. The plasma treatment device according to claim 1 further
comprising an electric, pneumatic or hydraulic drive unit, which is
coupled to the at least one movably mounted electrode, or to the
cylinder or carrier element carrying the at least one movably
mounted electrode for the purpose of moving the at least one
movably mounted electrode.
4. The plasma treatment device according to claim 1 wherein the at
least one movably mounted electrode, or a cylinder or carrier
element carrying the at least one movably mounted electrode, has a
surface contour that drives the at least one movably mounted
electrode rotationally by routing a gas stream over the surface
contour.
5. The plasma treatment device according to claim 1 further
comprising a handle in which the electrode arrangement is
integrated.
6. The plasma treatment device according to claim 1 wherein the
plasma is a cold-atmospheric pressure plasma.
Description
FIELD OF THE INVENTION
The invention relates to a plasma treatment device, having an
electrode arrangement for generating a plasma, in particular a cold
atmospheric-pressure plasma.
The invention additionally relates to a method for plasma treatment
of a surface by means of such a plasma treatment device.
BACKGROUND
Besides solid, liquid and gaseous, plasma is the fourth state of
aggregation of matter. It can be used, in the form of a
low-temperature plasma, as at least partially ionized gas, for
numerous applications for treating surfaces. Thus, surface
activation is conceivable, but so too is surface cleaning, owing to
the disinfecting/sterilizing action of low-temperature plasma.
DE 10 2006 019 664 A1 describes a cold-plasma handheld device for
plasma treatment of surfaces. A high-voltage unit, having an
adaptation network for generating the high voltage required for
producing plasma, is built into a handle, or handheld casing. A
process gas is routed through the high-voltage unit. The plasma jet
that is produced after passage through the high-voltage generator
is driven outward by the gas stream, and emerges in a relatively
highly focused manner. In order to widen the plasma stream, the
plasma nozzle can be widened and provided with a slot.
DE 10 2009 028 190 A1 discloses a plasma handheld device having an
integrated high-frequency generator, and having a gas inlet for
supplying process gas. Again, a plasma jet, driven by the process
gas, emerges from a nozzle at the outside-face end of the plasma
handheld device. Since the plasma nozzle, the high-voltage source
and a high-frequency generator are integrated into the easily
handled plasma tool, the spurious electromagnetic radiation is
reduced. For differing plasma beams, various types of electrode may
be provided, such as needle-shaped electrodes, blade-shaped
electrodes, or a plurality of needle-shaped electrodes arranged
next to each other.
DE 10 2009 047 220 A1 describes an appliance and a method for
generating a pulsed, cold atmospheric-pressure plasma for
antimicrobial plasma treatment (sanitization, disinfection,
sterilization, decontamination) of extremely small surfaces and
cavities, with pinpoint precision. A process gas is introduced into
a handheld device via a gas inlet, and routed through a
high-voltage electrode for the purpose of ionization. The
electrically conductive object to be treated serves as a
counter-electrode. In order to enlarge the receiving plane, a
parallel circuit of a plurality of electrodes can be provided for
the purpose of upscaling.
CN 101778525 A describes a pneumatically rotatable air plasma jet
source, in which a plasma jet flows out of a rotatable, obliquely
oriented nozzle.
SUMMARY
Proceeding therefrom, it is an object of the present invention to
create an improved plasma treatment device and an improved method
for plasma treatment of a surface by means of such a plasma
treatment device, in which the surface area receiving the plasma
jet is enlarged and the treatment time is thereby reduced, with the
structure and handling being as simple as possible.
It is proposed that the electrode arrangement of the plasma
treatment device have at least one movably mounted electrode, and
the plasma can be generated so as to vary in location, by means of
movement of the at least one electrode.
The ignition region between the effectively active portion of the
moving electrode and a counter-electrode, which may also be an
electrically conductive object to be treated, can be varied
continuously as a result of the continuous, automatic movement of
the at least one electrode. Thus, with the plasma treatment device
oriented in an unchanging manner onto the surface to be treated,
the surface area that receives the stream of plasma gas and that is
thereby treated is thus enlarged, the as compared with the
stationary electrode in the case of a stationary plasma treatment
device.
Whereas, in the prior art, the surface area receiving the stream of
plasma gas is enlarged by widening of the nozzle head, e.g. by
means of a slot or by parallel connection with associated nozzles,
or by movement of the nozzle head, the present invention proposes a
driven movement of the electrode arrangement. Thus, with the plasma
treatment device oriented in a stationary manner onto the surface
to be treated, the surface area receiving the generated plasma
stream is thus already enlarged the instant the ignition spark is
generated, and not as a result of a subsequent orientation of the
stream of plasma gas. This has the advantage that a plasma
generated in a gas stream that is passed through can easily act
upon the gas stream over a large area as it flows through.
This, however, does not preclude the outflowing stream of plasma
gas from also additionally being distributed further, for example
by a rotating nozzle head.
The electrode may be moved in a linear manner, in a rotatory
manner, with a plurality of superimposed movement directions, or in
another appropriate manner.
The movably mounted electrode is preferably the electrode to which
high-voltage potential is applied, and that is disposed adjacently
to a counter-electrode connected to frame potential. This
counter-electrode may be part of the electrode arrangement in the
plasma treatment device. It is also conceivable, however, for the
counter-electrode to be constituted by the surface to be treated.
The conductive counter-electrode may thus be constituted, for
example, by a fluid such as, for example, water.
In a preferred embodiment, which is very easy to handle, the
electrode arrangement preferably has a rotatably disposed cylinder.
The at least one electrode is then realized as a conductor path or
conductor wire disposed in the form of a spiral on the cylinder.
The conductor path may be, for example, materially bonded to the
cylinder surface. It is also conceivable, however, for a conductor
wire or an electrically conductive strip of material to be wound
around the surface of the cylinder. Disposed on the cylinder is
also understood to mean, however, that the conductor paths or the
conductor wire are immersed in the cylinder, at least partially. It
is thus conceivable for the cylinder to have at least one groove,
wound in the form of a spiral, in which an electrically conductive
conductor path or such a conductor wire is inserted.
Owing to the rotation of the cylinder that carries the conductor
path or conductor wire in the form of a spiral, the ignition region
between a point on the conductor path, or conductor wire, and the
nearest region of the counter-electrode, respectively, is altered
continuously in its position. This has the result that the ignition
sparks produced when high-voltage potential is applied to the at
least one electrode shift continuously as the cylinder rotates, and
change their location. Consequently, in the case of a plasma
treatment device that is fixed relative to the treating surface,
for example if the surface to be treated constitutes the
counter-electrode, a larger surface area is treated by the
generated plasma, along the cylinder length in the direction of
extent of the cylinder, as compared with the stationary
electrode.
It is also conceivable, however, for the electrode arrangement to
have a counter-electrode that surrounds the cylinder at a distance.
In this case, a gas supply connected in a communicating manner to
the interspace between the cylinder and the counter-electrode
surrounding the cylinder, in order to route a gas stream into the
interspace. Owing to the rotation of the cylinder carrying the at
least one conductor path or conductor wire in the form of a spiral,
a plasma is generated, virtually in the entire space between the
cylinder surface and an adjacent inner wall of the
counter-electrode, by the ignition sparks generated with a
continuous change in location. Flowing through this space is the
gas stream, which is ionized by the ignition sparks. There is thus
generated, over a large area, a stream of plasma gas that flows out
of the space between the cylinder and counter-electrode through
which flow is effected. This stream of plasma gas does not have to
be highly focused, as in the case of conventional plasma gas
generation, and can be applied directly to a greater surface area
without the necessity of spreading out a focused gas stream. This
is due to the fact that the plasma is generated so as to vary in
location in the gas stream, and consequently a greater volume of
the stream of plasma gas can be ionized.
The counter-electrode in this case is preferably tubular and
concentrically surrounds the cylinder carrying at least one
electrode. It is also conceivable, however, for the
counter-electrode to surround only a partial circumference of the
cylinder. In another preferred embodiment, at least one rod
electrode is disposed on a rotatable carrier element disposed about
a rotation axis. The rod electrode in this case extends, in an
offset manner in relation to the rotation axis, in a direction
parallel to the rotation axis or at an acute angle in relation to
the rotation axis. Whereas, in the case of the first embodiment,
the at least one electrode acts at the circumference of a rotating
cylinder, in the case of this embodiment the rod electrode is
disposed at the end face of the rotatable carrier element. The rod
electrode can thus act at the head of a handheld casing of the
plasma treatment device, where it causes an ignition spark for
generating plasma by means of a counter-electrode disposed
adjacently to the free end of the rod electrode, when high-voltage
potential is applied to the rod electrode. Owing to the rotation of
the carrier element about a rotation axis, the tip of the rod
electrode describes an orbit about the rotation axis. This orbit
may be concentric in relation to the rotation axis, but need not
necessarily be so. An elliptic orbit is also conceivable if there
is a further motion, beyond the rotation about the rotation axis of
the carrier element, superimposed on the rod electrode. It is
particularly advantageous if the tip of the rod electrode is used
as an active portion for generating the plasma ignition spark. For
this purpose, a counter-electrode is then disposed adjacently to
the tip of the at least one rod electrode. This counter-electrode
may be either the surface of the object to be treated, which is
preferably at frame potential. It is also conceivable, however, for
the counter-electrode to be built into the plasma treatment device,
as part of the electrode arrangement.
It is particularly advantageous if the counter-electrode is
realized as a plate having a plurality of openings, the plurality
of openings being disposed in a distributed manner on at least one
orbit, which is matched, respectively, to the orbit of the tip of
the at least one rod electrode. In the case of disposition of a
plurality of rod electrodes, openings matched to the respective rod
electrodes may be provided on differing orbits.
If the rod electrode is then rotated about the rotation axis of the
carrier element, and the plate-type counter-electrode is disposed,
approximately perpendicularly in relation to the rotation axis,
adjacently to the tip of the at least one rod electrode, then, upon
the rotational motion, the tip of the rod electrode will
periodically be oriented onto one of the openings in the plate.
Then, with a high voltage being continuously applied to the rod
electrode, an ignition spark is generated when the tip of the rod
electrode sweeps over the opening. This ignition spark is then
extinguished again when the rod electrode is positioned closer to
the electrically conductive material of the counter-electrode
plate. Besides making it possible to dispense with ignition control
electronics, this self-ignition by means of a rotating rod
electrode also makes it possible to reduce the temperature of the
stream of plasma gas that is generated.
For this self-ignition without additional control electronics, it
is advantageous if the counter-electrode is composed of a
dielectric material. The at least one rod electrode can then be
supplied by means of a DC high-voltage source (direct voltage) or,
preferably, by means of a high-frequency high-voltage source in the
MHz range. In the case of a dielectric counter-electrode, the MHz
high-voltage supply improves the self-ignition and ensures that the
generated plasma is of a sufficiently low temperature not to affect
a surface by the effect of temperature as the surface is being
treated.
The plasma treatment device preferably has an electric, pneumatic
or hydraulic drive unit, which is coupled directly to the at least
one electrode, or to the cylinder or carrier element carrying the
electrode, for the purpose of movement. The at least one electrode
is thereby put into a rotational motion, for example by means of an
electric motor, such that, by means of the drive unit, the plasma
is generated so as to vary in location.
It is also conceivable, however, for the at least one electrode, or
a cylinder or carrier element carrying the at least one electrode,
to have a surface contour that is realized to drive the at least
one electrode rotationally by routing a gas stream over the surface
contour. The surface contour may have, for example, spiral
depressions or protuberances. The gas stream flowing into the
plasma treatment device, in which a plasma is generated by
ionization by means of ignition sparks, and which then flows out of
the plasma treatment device, as a stream of plasma gas, may be used
as a gas stream. This gas stream is then routed along the surface
contour, and thereby effects a rotational motion. Thus, for
example, a cylinder carrying the at least one electrode, or a
carrier element carrying the at least one electrode, may be
designed as a drive element, by means of contouring, in order for
the latter to be put into a rotational motion by the gas stream.
There is then no longer a requirement for a separate drive unit.
The plasma treatment device can thus be of a very simple and
compact construction.
The plasma treatment device preferably has a handle, in which the
electrode arrangement is integrated. The plasma treatment device
may thus have, for example, a tubular casing, which serves as a
casing for the electrode arrangement and constitutes the
handle.
DESCRIPTION OF THE DRAWINGS
The invention is explained in greater detail in the following on
the basis of exemplary embodiments, together with the appended
drawings. These show:
FIG. 1--Diagram of a first embodiment of a plasma treatment device,
having a rotatable rod electrode;
FIG. 2a--Diagram of a second embodiment of a plasma treatment
device, having a spiral electrode on a rotatable cylinder, adjacent
to a planar surface to be treated, as a counter-electrode, in a
first position;
FIG. 2b--Diagram of a second embodiment of a plasma treatment
device, having a spiral electrode on a rotatable cylinder, adjacent
to a planar surface to be treated, as a counter-electrode, in a
second position;
FIG. 3--Diagram of a second embodiment of a plasma treatment
device, having a spiral electrode on a rotatable cylinder, adjacent
to a planar surface to be treated, as a counter-electrode, at high
rotational speed;
FIG. 4--Diagram of a third embodiment of a plasma treatment device,
having a rotatable cylinder carrying a spiral electrode, having a
surrounded tubular counter-electrode.
DESCRIPTION
FIG. 1 shows a diagram of a plasma treatment device 1, having a
handheld casing 2. Built into the interior of the handheld casing 2
there is an electrode arrangement 3, which is supplied with a high
voltage from a high-voltage source 4. The electrode arrangement 3
has a rod electrode 5, which is disposed at the end face of a
rotatably disposed carrier element 6. The carrier element 6 is, for
example, a cylinder, extending in a direction of longitudinal
extent and having a circular end face at an end that carries the at
least one rod electrode 5. A single rod electrode is represented.
It is also conceivable, however, for two, three or more rod
electrodes to be disposed at the end face. The at least one rod
electrode 5 is connected in an electrically conducting manner to
the high-voltage source 4 and, when in operation, is at
high-voltage potential. Disposed adjacently to the free end of the
at least one rod electrode 5 there is a counter-electrode 7, as
part of the electrode arrangement 3. This counter-electrode is
likewise connected to the high-voltage source 4, and is preferably
at frame potential during operation. It can be seen that the
plate-type counter-electrode 7 has openings 8 disposed in a
distributed manner over an orbit. This orbit corresponds to the
orbit of the tip of the rod electrode 5 when the latter moves about
the rotation axis R of the carrier element 6 as a result of the
rotation of the carrier element 6. In the exemplary embodiment
represented, the at least one rod electrode 5 extends parallelwise
in relation to the direction of extent of the rotation axis R. It
is also conceivable, however, for the rod electrode 5 to be set
obliquely thereto, and to be at an acute angle, preferably in the
range of from 0 to 45 degrees, in relation to the rotation axis.
The surface area that is swept by the at least one rod electrode 5
can thus be enlarged, if necessary, without enlarging the
circumference of the carrier element 6.
The carrier element 6 is coupled to a drive unit 9. This drive unit
9 may be, for example, an electric motor. It is also conceivable,
however, for the drive unit 9 to be a pneumatically operated motor.
In this case, advantageously, a gas stream G, which is introduced
into the plasma treatment device 1 and which flows out of the
openings 8 of the counter-electrode 7, can be used.
Irrespective of the drive unit 9, in the exemplary embodiment
represented the plasma treatment device 1 has a gas inlet 10 for
letting in the gas stream G, which is then routed along the carrier
element 6 to the region between the electrode arrangement 3. When
the rod electrode 5 sweeps with its free end over the opening 8 in
the counter-electrode 7, a respective ignition spark is then
generated, which ionizes the gas stream and results in a stream of
plasma gas. This stream of plasma gas P then emerges from the
openings 8 of the counter-electrode 7 and is routed onto the
surface 11 to be treated. With the plasma treatment device 1 kept
constantly oriented onto the surface 11, or object, to be treated,
a receiving treated surface area 12 is enlarged, as compared with a
focused plasma beam. This is achieved by generating the stream of
plasma gas P in a spread-out manner, which is effected by rotation
of the rod electrode 5 in the direction of the arrow, about the
rotation axis R, in that the ignition spark and the plasma are
generated so as to vary in location.
Inert gases, air or the like are suitable for the gas stream G.
FIG. 2a shows a diagram of a second embodiment of a plasma
treatment device 1, in a perspective arrangement. The plasma
treatment device 1 has a rotatably disposed cylinder 13. On its
surface, the cylinder 13 has electrodes 14, in the form of
conductor paths or conductor wires, which go around the curved
surface of the cylinder and which are wound around the cylinder 13.
The at least one electrode 14 is again connected to a high-voltage
source 4 and, when in operation, is at high-voltage potential. A
plurality of electrodes 14, wound in the form of a spiral and
disposed next to each other, may be electrically connected in
parallel in this case.
The cylinder 13 is disposed adjacently to a, for example,
plate-type counter-electrode 15, which is likewise connected to the
high-voltage source 4 and is preferably at frame potential. The
counter-electrode 15 may be, for example, the surface of the object
to be treated. When high voltage is applied to the electrode 14, a
respective ignition spark, and consequently a plasma, is generated
at the regions of the spiral electrode path that is nearest to the
surface to be treated, or to the counter-electrode 15.
If the cylinder 13 is now made to rotate slowly about the rotation
axis R, new ignition sparks are then continuously produced at other
locations, depending on the position of the regions of the
electrode 14 that is nearest the counter-electrode 15. Owing to the
spiral winding of the electrode around the cylinder surface, the
ignition sparks thus move along the surface of the
counter-electrode 15. Thus, with a constant orientation of the
cylinder 13, or of the plasma treatment device 1, onto the surface
to be treated, or onto the counter-electrode 15, the rotation of
the cylinder 13 causes a plasma to be applied to a region over the
length, in the direction of extent, of the cylinder 13.
If the cylinder 13 is now put into a rapid rotational motion, as
illustrated in FIG. 3, the ignition sparks 16 are generated over a
relatively short time in virtually the entire space. Further
ignition sparks are produced adjacently to the ignition spark
generated a short time before, such that a plasma is applied
virtually simultaneously to the surface of the object 15 to be
treated, virtually over this entire effective length of the
cylinder 13. During the treatment, the cylinder 13 can now be moved
transversely in relation to the direction of longitudinal extent of
the cylinder 13, in order thereby to treat a relatively large
surface area with plasma in a short period of time. It is also
conceivable for a plurality of devices to be connected next to each
other (array connection), in order to treat an even greater surface
area.
FIG. 4 shows a third embodiment of a plasma treatment device 1. The
plasma treatment device 1 has an electrode arrangement 3, which is
composed of at least one electrode 14, to which high voltage is
applied during operation, and of a counter-electrode 17. As in the
second exemplary embodiment, the at least one electrode 14 is again
disposed so as to go around the surface of a rotatable cylinder 13.
A cylinder is to be understood to mean, in principle, a carrier
element, extending in a direction of main extent, having a curved
or at least polygonal surface.
The counter-electrode 17 is a tubular entity concentrically
surrounded the cylinder 13. The counter-electrode 17 is also
connected in an electrically conducting manner to the voltage
source 4, and is preferably at frame potential. As a result of high
voltage being applied to the electrode 14, ignition sparks 16 are
then generated between ignition regions of the electrode 14 and the
nearest region of the inner wall of the counter-electrode 17. These
ignition sparks 16 result in a plasma in a gas stream G, which is
routed, through an inlet 10, into the interspace Z between the
cylinder 13 and the inner wall of the counter-electrode 17. The
resultant stream of plasma gas P is then routed out at the end-face
outlet of the plasma treatment device 1. In this case, the tubular
counter-electrode 17 may also simultaneously constitute the
handheld casing. It is also conceivable, however, for the tubular
counter-electrode 17 to be surrounded by a handheld casing, for
example of plastic material, the stream of plasma gas P then
emerging from the end face thereof.
Optionally, a more or less focused or additionally rotatable
nozzle, for deflecting the stream of plasma gas P flowing out, may
also be provided at the end-face outlet of the plasma treatment
device 1.
The plasma treatment device 1 is then oriented onto the surface 15
to be treated, such that the stream of plasma gas is incident upon
a surface area 12 treated with plasma.
The rotation of the electrodes 14 is preferably effected by a drive
unit 9. The latter may be realized as an electric drive unit (for
example, electric motor) or as a pneumatic or hydraulic drive unit.
The drive unit 9 may thus be driven, for example, by means of the
gas stream G that is supplied in any case.
In the case of the embodiments described, it is crucial that the
electrodes 14 move, in order thus to generate the at least one
ignition spark 16 and to generate the plasma, produced as a result
of this, so as to vary in location. As a result of this, the
effective plasma volume, or the effective plasma area, is enlarged,
the position of the plasma treatment device 1 being otherwise
constant. In the generation of plasma, therefore, the efficiency of
the plasma treatment device is already increased by movement of the
electrodes, and not just by variation of the location of the
already generated stream of plasma gas.
* * * * *